Asbestos fibers are split into two mineral groups serpentine which only includes chrysotile asbestos and amphibole which includes the other five varieties. Asbestos mineral formations are found throughout the world with major deposits located in Africa, Russia, South Asia, Australia and Canada.
All forms of asbestos are classified as silicates meaning they contain both silicon and oxygen. There are about 30 varieties of these minerals and silicates make up nearly 90 percent of the earth’s crust. What makes asbestiform different than other minerals is that it tends to grow fibers which were then harvested and used in industrial applications.
Chrysotile is the only form of asbestos still in commercial use today. Often the material is exported in large sheets and used as a cheap building material for third world countries which continues the terrible legacy of asbestos.
Chrysotile Asbestos (also referred to as white asbestos)
Chrysotile is the fibrous variety of serpentine and the only asbestiform from that group. Large chrysotile formations can be found throughout the world including Brazil, Canada, China, Russia, and Zimbabwe. Many of those countries continue to actively mine chrysotile and in 2006, over 2 megatons of raw chrysotile was exported throughout the world.
Chrysotile has been used in production more than any other form od asbestos and one estimate claims that 95 percent of buildings in the United States contaminated with asbestos contain the chrysotile form. Part of the popularity of Chrysotile is that the fibers are curly as opposed to the more needle-like fibers from the amphibole varieties. Since it is more flexible it can be used for a wider variety of industrial applications and can be woven into fabric.
Common uses of chrysotile include asbestos cement where it is manufactured into corrugated sheets, insulation, gaskets and high friction parts like brake pads.
A common defense for the continued use of chrysotile fibers is that they are considered far less toxic than fibers from other varieties of asbestos. There is evidence for this claim but less toxic does not mean it is safe cannot and many countries including the United States consider it a human carcinogen.
Amosite (also referred to as brown asbestos)
Amosite is a rare fibrous form of grunerite commonly found in South Africa and the name itself is an acronym for Asbestos Mines of South Africa. It was commonly used in pipe insulation (including many US Navy ships), asbestos cement and as an additive to some plastics.
Material Safety Data Sheet for Amosite Asbestos.
Crocidolite (also referred to as blue asbestos)
Crocidolite is the fibrous form of riebeckite found primarily in Africa and Australia. It was mainly used to insulate pipes and commercial ovens.
The town of Wittenoom, AU was closed in 1966 following concerns about contamination and the death toll from exposure to crocidolite is expected to be over 2,000.
Crocidolite contamination from abandoned mines in South Africa continues to claim lives and in response the government began a large scale cleanup project of mine tailings.
The next three forms of asbestos were not commonly used for industrial applications but may still be present in some industrial and consumer products.
Actinolite forms as the product of metamorphasis of magnesium rich limestones and the fibrous form of actinolite is an asbestiform.Byssolite is an asbestiform hair like variety of actinolite featuring tiny interwoven crystals that grows in western Europe and along the eastern and western coasts of north America.
Actinolite has large formations in Russia, China, New Zealand, Canada and Tawian.
Anthophyllite is formed by the breakdown of talc in rock formations and is often found in the same mines as talc. Talc is commonly used in chalks and cosmetics and companies have been forced to change their production of goods to ensure that asbestos content is greatly reduced or removed altogether. One study attributed cases of mesothelioma to exposure in talc mines but those workers had additional risk factors as well.
Tremolite was not commonly used as a direct material but it is the form of asbestos that contaminated the vermiculite used for zonolite insulation. In Libby alone, exposure to tremolite asbestos has been blamed for nearly 2,000 cases of asbestos related deaths or illnesses as a result of the contamination. Homeowners who may have zonolite in their attic are urged not to disturb the material.
Winchite is not currently regulated as an asbestiform but fibrous samples of it have been found in the vermiculite mine in Libby often with trace amounts of crocidolite.